Availability of Aluminum Phosphate from Alum-Treated Wastewater for Algal Growth,

摘要

For phosphorus removal from wastewater,alum coagulation-precipitation is often the removal method of choice. Typically,alum is added ahead of the final settling tank in a ratio of 1.8aluminum to 1phosphorus. At this ratio phosphorus precipitates as an AlPO4complex associated with coagulated Al(OH)n,species. While most (80-90%) of the phosphorus is removed by settling,some carries over into the effluent. Only 10% of the carryover phosphorus is filterable;therefore 90% is in a particulate form. This research explored the availability of this particulate phosphorus in a pure chemical system,an open-channel,mixed-culture system (stream channel study),and a unialgal,batch-culture system (bioassay study). Growth of the test alga, Selenastrum capricornutum was not inhibited by Al(+3). When the concentration of total phosphorus (in alum-flocculated form) was 0.5mg/l,growth was equivalent to that with an equivalent concentration as K2HPO4. However,when the total phosphorus (as alum-flocculated phosphate) was 0.186mg/l,growth was less than that with an equivalent amount as K2HPO4.